Seriously, you need to look at how you will be using the instrument, budget, the sounds you want (or can create, if applicable). then go and play them at the local music shop. (bring your own headphones or in-ear monitor)

I Had a Korg poly6 and the battery leaked onto the cicuit board and destroyed it. Some of the notes had quit working before that. I had a Korg M1, the battery went dead without warning and I lost all the settings and songs that were in it that I worked so hard on. It did not feel nice to play. I have Roland A500pro,Roland SonicCell, Roland Vk8m organ, and 2 M-Audio controllers. I had a Roland Ms64 that I traded for a decent guitar.
NEVER have I had a problem with Roland and I Always had trouble with the Korgs. I can't afford things that are unreliable. That is why I did not spend my hard earned dollars on the Triton. Oh ya, I am still playing a Roland A-37 that is at least 10 years old and I pound it everyday and carry around everywhere I go. It's my easiest controller to set up.
Roland or Korg. I also had a Korg guitar tuner that went for a crap.
That is just one mans opinion based on facts.

Keyboard Player. NorthEast of Toronto, Beaverton area, seeking to join or start new band

I haven't experienced any problems with the couple of Korg keyboards I've owned. Rolands are reliable too but I think the programming is a bit clunky. Once I learned the Korg system I found it pretty easy to make quick edits and tweaks. And Oh, the sound. To my ear the Korgs just have a richer more interesting sound, especially with the motion/evolving type presets. Don't get me wrong, I love my Roland gear as well even though it is some older (JV) gear. I guess you really should have one of each, plus some others too while your at it. Each manufacturer has something different from the other to go along with all the generic piano, brass, strings,etc. The more the merrier I say.

I have played many of the vintage and other keyboards
My brother owns Most of them
For actual old type synth sounds the top of the line is OB 6
according to Him and I have not heard anything that could dispute that
For samplers and you really need one synth and one Sampler
the 3 best are (not in any particular order)
Oldest Kurzweil K2500 or 2600 with sample option
easiest and cheapest to obtain
I own 3 of these 1 keybord and 2 rackmounts
the Fantom G6,7,or8 by Roland
same thing maybe easier to use a little
But the price tag is 3 times the first
and The Korg OAASYS and It does a Lot more than I have knowledge of
Price tag very High as well
You can get a Kurzweil used pretty cheap now
if you need bang for Buck that would be My first choice
as far as a synth you could in a pinch use yuor computer soft synth's and sample them
Best of luck

I like the Roland Fantom X6, however I find the Black keys are a little narrow, and my fingers slid off until I got used to it.

I also play a Yamaha M06, but Don't bother getting one of those. The M06 has a poor key feel. I got one for a very low price, and use it as a back-up keyboard. If the Roland breaks down, the show must go on.

I also play a Vintage Rhodes 76 stage elec piano, for that one, you better practice your wrist action to get sound.

Me personally- I like BOTH...I have a trinity v3 fully outfitted with the hdr and pbs-tri expansion boards fitted,and use a roland fantom g6 with the arx elec pianos and the brass expansion(love that one)...

The Korg is much more intricate and better with it's airy/dreamy type patches,and the roland seems like it's more geared towards dance phrases and good syncopated rhythm stuff. I love both! What I don't have I will sample it into the fantom if I want it that bad...(They probably wouldn't like it if I brought my fantom into the nearest guitar center and started sampling all the different keyboards I liked!

Virtual Analog, both makers have solid instruments that fill that capacity.

Workstations again both are solid, I have a Fantom G6 and its a wonderful instrument, with that said the Korg Oasys is amazing.

Romplers, performance keyboards that have ROM based waveforms that cover the entire range of instrument reproductions. My personal preference in this area is Roland. I think Roland has some nice pianos and orchestral tones, the old JV and XP Rolands are great all around boards. Dont count out the Yamaha boards in this category either.

It's interesting. I own both and one observation is this. When I listen to the sounds of each individually, I tend toward the Roland, however, for playing live, the Korg is much punchier and percussive. Now I predominately play the piano sounds. I own a Korg triton studio 88 and I've owned several Roland e pianos and synths

GETTING ONE OF EACH IS A GOOD IDEA IF IT IS FEASABLE. I HAVE A KORG STAGE PIANO , WHICH IS A VERY SUBSTANTIAL KEYBOARD, I ALSO HAVE TWO ROLAND SYNTHS. THE OLD D50 WHICH IS GREAT FOR PLAYING OLD R&B AND EARLY ROCK AND ROLL, AND A NEW VR09 FOR GREAT NEW SOUNDS INCLUDING SEVERAL KILLER ORGAN SOUNDS THAT RIVAL MY HAMMOND XK3 WITH OUT HAVING TO BRING ALONG A LESLIE ALSO IT HAS A BUILT IN DRUM MACHINE WITH NEWER TEMPOS AND SOUNDS AND IT ONLY WEIGHS 12 POUNDS AND IS A LOT EASIER TO MOVE IT TO A GIG THEN ANY OTHER KEYBOARD THAT I HAVE OWNED. I BELIEVE THAT YOUR DECISION WILL COME FROM THE TYPE OF MUSIC YOU WANT TO PLAY AND THE PORTABILITY OF YOUR BOARD. TRY TO REMEMBER THAT ONE KEYBOARD CANNOT DO IT ALL. BECAUSE YOUR MUSIC CHOICES AND STYLE CONTINUOUSLY CHANGES. AT LEAST MINE DOES. GOOD LUCK IN YOUR CHOICES.